Annulus fracturing gas lift fluid discharge pipe string and operation method

Abstract

The application discloses a kind of annular fracturing gas lift liquid discharge pipe columns and operating methods, including multiple groups of gas lift tools and throttling tools, when annular injection gas, gas enters cavity from the gap between the body of gas lift tool and gland, when injection pressure is greater than the pressure in gas cavity, lower valve body is pushed up, and the disengagement between upper ball valve and bidirectional valve seat, injection gas enters the tubing through bidirectional valve seat, and the liquid in the tubing is discharged by the gas lift tool;When injection pressure is lower than the pressure in gas cavity, upper ball valve is seated in bidirectional valve seat, and oil, casing passage is blocked, injection gas pushes annular fluid surface down, and the process of lower gas lift tool is repeated to open the liquid discharge operation, until the liquid in the tubing is discharged completely by the lowermost gas lift tool.The pipe column can realize rapid liquid discharge after fracturing, without well killing, down liquid discharge pipe column completion, avoid the damage to reservoir by well killing, ensure the modification effect, effectively improve the construction efficiency, reduce the operation cost.

Description

Technical Field

[0001] This invention belongs to the field of gas field fracturing technology, and relates to an annular fracturing gas lift drainage tubing and operation method. Background Technology

[0002] In the oil and gas field industry, fracturing refers to the artificial creation of fractures in underground rock formations to improve the flow environment of oil and gas underground and increase oil and gas production. High-volume fracturing can effectively increase the production of tight gas in a single well. However, some low-production wells face difficulties in draining fluid after fracturing and require auxiliary measures. Currently, the common practice is to complete the well by killing the well and (replacing) the draining tubing string after fracturing, which has the problems of low construction efficiency and significant damage to the reservoir from well killing. Annular fracturing gas lift draining tubing can meet the integrated construction needs of low-production wells for post-fracturing fluid draining. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a drainage string and operation method for a gas lift tool used in annular fracturing. The gas lift tool is lowered into the fracturing string, and after annular fracturing, annular air lift drainage enables rapid drainage of fluid after gas well fracturing. This eliminates the need for well control and replacement of the drainage string after fracturing, avoiding damage to the reservoir caused by well control, effectively improving construction efficiency, and reducing operating costs.

[0004] This invention is achieved through the following technical solution:

[0005] An annular fracturing gas lift drainage string, the drainage string includes a multi-stage gas lift tool and a throttling tool, the gas lift tools are connected sequentially by tubing, and the end of the last stage gas lift tool is connected to the throttling tool by tubing.

[0006] The air lift tool includes a tool body, a valve stem, and a pressure cap;

[0007] The tool body includes an eccentric inner hole, a single-flow valve ball seat hole, a body through hole, and a cavity;

[0008] The cavity is located on one side of the tool body, the pressure cap covers the top of the cavity, the valve stem is installed inside the cavity, the one-way valve ball seat hole is located on the tool body, one end of the one-way valve ball seat hole is connected to the cavity, one end of the one-way valve ball seat hole is connected to the through hole of the body, the eccentric inner hole is located inside the tool body, and the through hole of the body is connected to the eccentric inner hole.

[0009] The valve stem includes an upper valve body, a middle valve body, a lower valve body, and a single-flow valve assembly;

[0010] One end of the upper valve body is sequentially connected to the middle valve body, the lower valve body, and the check valve assembly. A bellows is provided between the middle valve body and the lower valve body. The check valve ball seat hole is connected to the check valve assembly. A valve core is provided inside the upper valve body. A gas cavity is formed between the hollow parts of the upper valve body and the middle valve body and the lower valve body. The valve core is sealed at the gas port of the gas cavity.

[0011] Preferably, the one-way valve assembly includes an upper ball valve, a two-way valve seat, and a lower ball valve, with the upper ball valve and the lower ball valve respectively disposed at both ends of the two-way valve seat; one end of the upper ball valve is connected to the lower valve body, and the lower ball valve is disposed inside the ball seat hole of the one-way valve, which is connected to the two-way valve seat; a spring is provided at the bottom of the lower ball valve.

[0012] Preferably, the ball seat hole of the one-way valve and the two-way valve seat are connected by threads.

[0013] Preferably, the bellows is a U-shaped bellows made of Ni-Cu alloy; the valve core uses a double-stage sealing ring; and the upper valve body, middle valve body, and lower valve body are all made of 1Cr18Ni9Ti.

[0014] Preferably, a tail plug is provided at the other end of the upper valve body.

[0015] Preferably, the two ends of the bellows are welded to the boss of the middle valve body and the boss of the lower valve body, respectively.

[0016] Preferably, a conduit is provided between the middle valve body and the lower valve body, and the bellows is disposed inside the conduit.

[0017] Preferably, the cap is connected to the tool body by a nut.

[0018] Preferably, the tool body is provided with airtight buckles at both ends, and the two ends of the eccentric inner hole are connected to the airtight buckles.

[0019] A method for operating an annular fracturing gas lift fluid discharge string, comprising,

[0020] The fracturing process involves tubing injection, specifically: the throttling tool maintains the tubing pressure higher than the casing pressure, ensuring that the lower ball valves in the single-flow valve assemblies of all gas lift tools are seated in the lower end of the bidirectional valve seat, thus blocking the tubing and casing passages at all gas lift tools, thereby enabling normal annular fracturing.

[0021] Following fracturing, the fluid is discharged via staged gas lift. Specifically, when gas is injected into the annulus between the tubing and casing, the gas enters the cavity through the gap between the tool body and the gland in the uppermost gas lift tool of the discharge string. When the injected gas pressure is greater than the pressure inside the gas cavity, it pushes the lower valve body upward, the bellows contracts, and the upper ball valve in the one-way valve assembly disengages from the two-way valve seat. The injected gas then enters the tubing through the two-way valve seat in the one-way valve assembly, discharging the liquid from the body through-hole, the cavity, and the upper tubing of this stage of the gas lift tool. When the injected gas pressure is lower than the pressure inside the gas cavity, the upper ball valve in the one-way valve assembly sits into the two-way valve seat, blocking the tubing and casing passages. The injected gas pushes the annulus liquid level between the tubing and casing downward, and the next stage of the gas lift tool repeats the process of the previous stage to open and perform the fluid discharge operation until all the liquid in the tubing above the lowest stage of the gas lift tool is discharged.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This invention provides an annular fracturing gas lift fluid discharge string and operation method. During the fracturing process, the tubing pressure is controlled to be higher than the casing pressure by a choke tool. The resulting pressure difference between the oil and casing causes the one-way valve of the gas lift tool to close. During the fracturing process, the oil and casing are not connected at the gas lift tool, and annular fracturing is carried out. Compared with tubing fracturing, the discharge volume is larger. After fracturing, there is no need to kill the well or replace the fluid discharge string before gas lift fluid discharge and production can be started. This realizes rapid fluid discharge after large-volume annular fracturing of gas wells. The large-volume discharge has a good reservoir stimulation effect, avoids well killing, reduces reservoir damage, and further ensures the stimulation effect. At the same time, it effectively improves construction efficiency and reduces operating costs.

[0024] The operation method of the annular fracturing gas lift fluid discharge string of the present invention is simple. Fracturing is completed by controlling the tubing pressure to be higher than the casing pressure, and the fluid is discharged by gas lift in stages after fracturing.

[0025] Furthermore, the bellows of this invention is a U-shaped bellows made of multi-layer Ni-Cu alloy, and the valve core is a double-stage sealing ring, both of which are used to improve the pressure resistance of the valve stem and ensure the normal implementation of fracturing modification. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the annular fracturing gas lift tool structure of the present invention;

[0028] Figure 2This is a partial structural diagram of the annular fracturing gas lift tool body of the present invention;

[0029] Figure 3 This is a partial structural diagram of the air-lift tool body of the present invention.

[0030] Figure 4 Figure (a) is a top view of the pressure cap and Figure (b) is a side view of the pressure cap.

[0031] Figure 5 This is a schematic diagram of the annular fracturing gas lift fluid discharge tubing of the present invention;

[0032] In the diagram: 1. Air lift tool; 2. Throttling tool; 11. Tool body; 12. Valve stem; 13. Pressure cap; 101. Eccentric inner hole; 102. One-way valve ball seat hole; 103. Body through hole; 104. Cavity; 105. Airtight fastener; 201. Tail plug; 202. Upper valve body; 203. Valve core; 204. Middle valve body; 205. Bellows; 206. Guide tube; 207. Lower valve body; 208. Upper ball valve; 209. Two-way valve seat; 210. Lower ball valve; 211. Spring. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0034] An annular fracturing gas lift discharge string, such as Figure 1 As shown, the air lift tool 1 includes a tool body 11, a valve stem 12, and a pressure cap 13;

[0035] like Figure 3 As shown, the tool body 11 includes an eccentric inner hole 101, a single-flow valve ball seat hole 102, a body through hole 103, and a cavity 104.

[0036] The cavity 104 is located on one side of the tool body 11, the pressure cap 13 covers the top of the cavity 104, the valve stem 12 is installed inside the cavity 104, and the one-way valve ball seat hole 102 is located on the tool body 11. One end of the one-way valve ball seat hole 102 is connected to the cavity 104, and the other end of the one-way valve ball seat hole 102 is connected to the body through hole 103. This invention forms a body flow channel inside the cavity 104 of the tool body, and a one-way valve assembly is installed inside the body flow channel to achieve unidirectional flow control of the fluid in the gas lift process. The use of the throttling tool ensures that the gas lift tool is closed during fracturing, and the oil jacket is not connected. At the same time, by improving the material and structure of the bellows, gas chamber, and valve core, the pressure resistance of the tool is improved, ensuring the normal implementation of fracturing modification. The tool body 11 has an eccentric inner hole 101 inside, and the body through hole 103 is connected to the eccentric inner hole 101 to form a gas flow passage. An eccentric inner hole 101 is axially disposed inside the center of the tool body 11, and a body through hole 103 is radially disposed on the tool body 11 near the cavity 104. A one-way valve ball seat hole 102 is axially disposed on the tool body 11 near the cavity 104. One end of the one-way valve ball seat hole 102 is connected to the cavity 104, and the other end of the one-way valve ball seat hole 102 is connected to the body through hole 103.

[0037] like Figure 2 As shown, the valve stem 12 includes an upper valve body 202, a middle valve body 204, a lower valve body 207, and a one-way valve assembly; the valve stem can withstand a pressure of not less than 70MPa, that is, the gas lift valve can work normally under the condition of a maximum fracturing pressure difference of 70MPa, so as to realize fracturing and gas lift.

[0038] One end of the upper valve body 202 is sequentially connected to the middle valve body 204, the lower valve body 207, and the check valve assembly. A bellows 205 is provided between the middle valve body 204 and the lower valve body 207. The check valve ball seat hole 102 is connected to the check valve assembly. A valve core 203 is provided inside the upper valve body 202. A gas chamber is formed between the hollow portion of the upper valve body 202 and the middle valve body 204 and the lower valve body 207, and the gas chamber is filled with nitrogen. The valve core 203 is sealed at the gas port of the gas chamber. The valve core is a double-stage sealing ring, both used to improve the pressure resistance of the valve stem.

[0039] The one-way valve assembly includes an upper ball valve 208, a two-way valve seat 209, and a lower ball valve 210. The upper ball valve 208 and the lower ball valve 210 are respectively disposed at both ends of the two-way valve seat 209. One end of the upper ball valve 208 is threadedly connected to the lower valve body 207. The lower ball valve 210 is disposed inside the one-way valve ball seat hole 102, which is connected to the two-way valve seat 209. A spring 211 is provided at the bottom of the lower ball valve 210.

[0040] The other end of the upper valve body 202 is provided with a tail plug 201. The tail plug 204 adopts a nut structure to fix the upper valve body 202.

[0041] The two ends of the bellows 205 are welded to the bosses of the middle valve body 204 and the lower valve body 207, respectively. The bellows is a U-shaped bellows made of multi-layer Ni-Cu alloy, and the lower valve body boss at the lower end of the bellows is designed with the gas chamber component made of 1Cr18Ni9Ti material.

[0042] In one preferred embodiment of the present invention, a conduit 206 is provided between the middle valve body 204 and the lower valve body 207. The conduit 206 is used to ensure that the movement trajectory of the lower valve body 207 does not deviate and damage the components. The bellows 205 is disposed inside the conduit 206. The conduit 206 is sleeved on the outside of the middle valve body 204 and the lower valve body 207 to ensure that the lower valve body 207 is centered and moved downwards, so that the upper valve ball 208 can sit in the bidirectional valve seat 209.

[0043] like Figure 4 As shown, Figure 4 a is a top view of the pressure cap 13. Figure 4 b is a side view of the pressure cap 13; the pressure cap 13 is connected to the tool body 11 by a nut, and the one-way valve ball seat hole 102 is connected to the two-way valve seat 209 by a thread.

[0044] The tool body 11 is provided with airtight buckles 105 at both ends, and the two ends of the eccentric inner hole 101 are connected to the airtight buckles 105. The airtight buckles 105 adopt airtight threaded threads to achieve a sealing effect against gas.

[0045] An annular fracturing gas lift discharge string, such as Figure 5 As shown, the system includes multiple gas lift tools 1 and throttling tools 2. The gas lift tools 1 are disposed inside the annular fracturing gas lift drainage string, and the throttling tools 2 are installed at the end of the annular fracturing gas lift drainage string. The gas lift tools 1 are connected to each other via tubing, and the gas lift tools 1 and throttling tools 2 are connected via tubing. The throttling tools 2 control the tubing pressure to be higher than the casing pressure to complete fracturing, followed by staged gas lift drainage. Preferably, the throttling tool of this invention is a throttling nozzle; the inner diameter of the throttling tool is smaller than the diameter of the annular fracturing gas lift drainage string.

[0046] A method for operating an annular fracturing gas lift drain tubing string includes, during fracturing, tubing injection: the throttling tool controls the tubing pressure to always be higher than the casing pressure, so that the lower ball valves of all gas lift tools are seated in the lower end of their bidirectional valve seats, the oil and casing channels at all gas lift tools are blocked, and normal fracturing is performed. After fracturing, the fluid is discharged through a series of gas lift stages. Specifically, when high-pressure gas is injected, it enters the cavity through the gap between the tool body and the gland in the uppermost gas lift tool of the discharge string. When the injection pressure is greater than the pressure inside the gas cavity, it pushes the lower valve body upward, the bellows contracts, and the upper ball valve in the one-way valve assembly disengages from the two-way valve seat. The injected gas enters the oil pipe through the two-way valve seat in the one-way valve assembly, discharging the liquid from the body through-hole, the cavity, and the oil pipe above this stage of the gas lift tool. When the injection pressure is lower than the pressure inside the gas cavity, the upper ball valve in the one-way valve assembly sits into the two-way valve seat, blocking the oil and casing passage. The injected gas pushes the annular liquid level downward, and the next stage of the gas lift tool repeats the process of the previous stage to open and perform the fluid discharge operation until all the liquid in the oil pipe above the lowest stage of the gas lift tool is discharged.

[0047] The present invention will now be described in detail with reference to embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

[0048] The following detailed descriptions are all illustrative of embodiments and are intended to provide a further detailed explanation of the present invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention.

[0049] Example 1

[0050] At least one gas lift tool 1 is connected to a fracturing tool string at different depths, and one throttling tool 3 is connected to the end of the tubing string. The air lift tool includes a tool body 11, a valve stem 12, and a pressure cap 13. The tool body includes an eccentric inner hole 101, gas-sealed threaded threads at both ends 105, a cavity 104 on the thicker side, and a pressure cap 13 covering the upper part. The valve stem 12 is installed in the cavity 104. From top to bottom, the following components are connected in sequence: a tail plug 201, an upper valve body 202, a middle valve body 203, a guide tube 206, and a two-way valve seat 209. The upper part of the lower valve body 207 is connected to the protruding part at the lower center of the middle valve body 204, and the lower end is connected to a ball valve 208. The valve core 203 is placed in the upper valve body 202 to seal the gas cavity formed by the upper valve body 202, the hollow middle valve body 204, and the lower valve body 207. The gas cavity is filled with nitrogen. The upper and lower ends of the bellows 205 are welded to the two protrusions adjacent to the middle valve body 204 and the lower valve body 207, respectively. The tool is characterized by having a one-way valve ball seat hole 102 axially centered on one side of the recessed cavity 104 of the tool body. A lower ball valve 210 and a spring 211 are installed from the inside out. A radial through hole 103 connects the one-way valve ball seat hole 102 to the eccentric inner hole 101 within the inner cavity of the tool body. The one-way valve ball seat hole 102 is threadedly connected to the lower end of a two-way valve seat 209. The inner diameter of the throttling tool 2 is smaller than the pipe diameter. Fracturing is completed by controlling the tubing pressure to be higher than the casing pressure using the throttling tool 2. After fracturing, the fluid is discharged through staged gas lift. Specifically, when injecting gas, the gas enters the cavity 104 through the gap between the tool body 11 and the pressure cap 13. It acts on the lower end face of the lower valve body 207 boss of the valve stem 12, pushing the middle valve body 204 of the valve stem 12 upward and the bellows 205 contract. If its upward thrust is greater than the pressure of the nitrogen-filled gas cavity formed by the valve core 203, the upper valve body 202, the hollow middle valve body 204, and the lower closed valve body 207, the bellows 205 contracts, the upper ball valve 208 disengages from the upper end of the two-way valve seat 209, and the injected gas enters the tubing through the two-way valve seat 209, discharging the liquid in the body through hole 103, the cavity 104, and the upper tubing above the gas lift tool, thereby reducing the density of the upper well fluid. When the injection pressure is lower than the pressure inside the gas chamber, the upper ball valve 208 sits in the two-way valve seat 209, the oil and casing passages are blocked, the injected gas pushes the annular liquid level down, and the next stage gas lift tool repeats the process of the previous stage gas lift tool to open and perform liquid drainage operation until all the liquid in the oil pipe above the lowest stage gas lift tool is discharged.

[0051] Example 2:

[0052] The bellows 205 is a U-shaped bellows made of multi-layer Ni-Cu alloy. The lower valve body 207 at the lower end of the bellows 205 has a boss design. The gas chamber is made of 1Cr18Ni9Ti. The valve core 203 is a double-stage sealing ring, all of which are used to improve the pressure resistance of the valve stem.

[0053] Example 3:

[0054] The valve stem can withstand a pressure of not less than 70MPa, meaning that the gas lift valve can work normally under the condition that the maximum pressure difference during fracturing is 70MPa, thus enabling one trip of the fracturing and gas lift tubing.

[0055] Example 4:

[0056] An annular fracturing gas lift fluid discharge string and its operation method, based on the tools involved in the above-mentioned annular fracturing gas lift fluid discharge string, includes the following steps:

[0057] Step 1: Control the tubing pressure to be higher than the casing pressure to complete the fracturing.

[0058] Step 2: After fracturing, fluid is removed by staged air lift.

[0059] In summary, the technical solution of this invention employs a tubing string including a gas lift tool and a choke tool. A one-way valve at the inner end of the flow channel of the gas lift tool body enables unidirectional flow of fluid during fracturing and gas lift control. The choke tool controls the tubing pressure to be higher than the casing pressure, causing the gas lift tool to close during fracturing and preventing communication between the tubing and casing. Simultaneously, by improving the materials and structure of the bellows, gas chamber, and valve core, the pressure resistance of the tool is enhanced, ensuring normal fracturing operations. The tool of this invention is run along with the fracturing tubing string. After fracturing, annular air lift and fluid discharge achieve rapid post-fracturing fluid discharge from the gas well, eliminating the need for well kill and (replacement) of the fluid discharge tubing string after fracturing, thus avoiding reservoir damage from well kill, effectively improving construction efficiency, and reducing operating costs.

[0060] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An annular fracturing gas lift drainage string, characterized in that, The drain tubing includes a multi-stage air lift tool and a throttling tool. Each stage of the air lift tool is connected to the other stage in sequence via an oil pipe. The end of the last stage air lift tool is connected to the throttling tool via an oil pipe. The air lift tool includes a tool body (11), a valve stem (12), and a pressure cap (13). The tool body (11) includes an eccentric inner hole (101), a single-flow valve ball seat hole (102), a body through hole (103), and a cavity (104). The cavity (104) is located on one side of the tool body (11), the pressure cap (13) covers the top of the cavity (104), the valve stem (12) is installed inside the cavity (104), the one-way valve ball seat hole (102) is located on the tool body (11), one end of the one-way valve ball seat hole (102) is connected to the cavity (104), one end of the one-way valve ball seat hole (102) is connected to the body through hole (103), the eccentric inner hole (101) is located inside the tool body (11), and the body through hole (103) is connected to the eccentric inner hole (101); The valve stem (12) includes an upper valve body (202), a middle valve body (204), a lower valve body (207), and a single-flow valve assembly; One end of the upper valve body (202) is sequentially connected to the middle valve body (204), the lower valve body (207), and the one-way valve assembly. A bellows (205) is provided between the middle valve body (204) and the lower valve body (207). The one-way valve ball seat hole (102) is connected to the one-way valve assembly. A valve core (203) is provided inside the upper valve body (202). A gas cavity is formed between the hollow part of the upper valve body (202) and the middle valve body (204) and the lower valve body (207). The valve core (203) is sealed at the gas port of the gas cavity. The one-way valve assembly includes an upper ball valve (208), a two-way valve seat (209), and a lower ball valve (210). The upper ball valve (208) and the lower ball valve (210) are respectively disposed at both ends of the two-way valve seat (209). One end of the upper ball valve (208) is connected to the lower valve body (207), and the lower ball valve (210) is disposed inside the one-way valve ball seat hole (102), which is connected to the two-way valve seat (209). A spring (211) is provided at the bottom of the lower ball valve (210). A conduit (206) is provided between the middle valve body (204) and the lower valve body (207), and the bellows (205) is provided inside the conduit (206).

2. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The single-flow valve ball seat hole (102) and the two-way valve seat (209) are connected by threads.

3. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The bellows (205) is a U-shaped bellows, and the material of the bellows (205) is Ni-Cu alloy; the valve core (203) adopts a double-stage sealing ring, and the upper valve body (202), the middle valve body (204) and the lower valve body (207) are all made of 1Cr18Ni9Ti.

4. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The other end of the upper valve body (202) is provided with a tail plug (201).

5. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The two ends of the bellows (205) are welded to the boss of the middle valve body (204) and the boss of the lower valve body (207), respectively.

6. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The pressure cap (13) is connected to the tool body (11) by a nut.

7. The annular fracturing gas lift drainage string according to claim 1, characterized in that, The tool body (11) is provided with airtight buckles (105) at both ends, and the two ends of the eccentric inner hole (101) are connected to the airtight buckles (105).

8. A method for operating an annular fracturing gas lift drainage string, characterized in that, Based on the annular fracturing gas lift drainage string according to any one of claims 1-7, it includes, The tubing injection during the fracturing process is as follows: the throttling tool (2) maintains the tubing pressure higher than the casing pressure, so that the lower ball valve (210) in the single-flow valve assembly of all the gas lift tools sits in the lower end of the two-way valve seat (209), and the tubing and casing passages at all gas lift tools are blocked, thereby performing annular fracturing. After fracturing, the fluid is discharged via staged gas lift. Specifically, when gas is injected into the annulus between the tubing and the casing, the gas enters the cavity (104) from the gap between the tool body (11) and the gland (13) of the uppermost gas lift tool in the discharge string. When the injected gas pressure is greater than the pressure inside the gas cavity, the lower valve body (207) is pushed upward, the bellows (205) contracts, and the upper ball valve (208) in the one-way valve assembly disengages from the two-way valve seat (209). The injected gas then passes through the two-way valve seat in the one-way valve assembly. The valve seat (209) enters the oil pipe, discharging the liquid from the body through hole (103), cavity (104), and upper oil pipe of the gas lift tool. When the injection pressure is lower than the pressure in the gas chamber, the upper ball valve (208) in the single-flow valve assembly sits in the two-way valve seat (209), blocking the oil pipe and casing passages. The injected gas pushes the annular liquid level between the oil pipe and casing downwards. The next stage gas lift tool repeats the process of the previous stage gas lift tool to open and perform liquid discharge operations until all the liquid in the oil pipe above the lowest stage gas lift tool is discharged.

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